Preparation method and preparation equipment of spherical porous manganous-manganic oxide
Technical Field
The invention belongs to the field of green processing and resource utilization of industrial non-hazardous solid wastes, and particularly relates to a preparation method and preparation equipment of spherical porous manganous-manganic oxide.
Background
Spinel type lithium manganate (LiMn2O4) has the advantages of rich resources, low cost, environmental friendliness, high discharge voltage, high resistance to large-current charge and discharge, good safety and the like, and is one of the most advantageous positive electrode materials of the lithium ion secondary battery.
In the prior art, manganous-manganic oxide is mainly used as a manganese source for synthesizing lithium manganate, and the chemical reaction equation of the manganous-manganic oxide for synthesizing the lithium manganate is as follows:
8Mn3O4+5O2+6Li2CO3=12LiMn2O4+6CO2
as can be seen from the reaction equation, a large amount of oxygen needs to be absorbed during the reaction process, and an adequate oxygen atmosphere is needed during sintering. During ordinary pressure industrial production lithium manganate, the general 25cm of thickness is piled up to the material, and oxygen generally can't diffuse to bottom reaction material fast, leads to the synthetic lithium manganate oxidation of bottom incomplete, and reaction time is longer. A solution is provided for a problem of insufficient oxygen in a bottom material patent ZL201711334815.3 composite manganous-manganic oxide for lithium manganate and an industrial preparation method thereof, but the patent does not relate to non-composite spherical manganous-manganic oxide which is beneficial to improving the tap density of lithium manganate.
A porous spherical manganous manganic oxide preparation method is introduced in foreign papers (Donglei Guo et al, Electrochemical performance of solid sphere LiMn2O4 with high tap density synthesized by porous sphere Mn3O4[ J ], Electrochemical micron Acta, 2014,123: 254-. Aiming at the problems, the inventor designs a preparation method and preparation equipment of porous spherical trimanganese tetroxide.
Disclosure of Invention
The invention provides a preparation method of spherical porous manganous-manganic oxide, which aims to solve the problem of insufficient oxygen diffusion of bottom materials of lithium manganate in industrial production and improve the tap density of lithium manganate. The manganous-manganic oxide prepared by the method is of a spherical structure, the interior of the manganous-manganic oxide is rich in a pore channel structure, the existence of the pore channel structure promotes the oxygen to be fully diffused when the lithium manganate is synthesized, even when the material stacking thickness reaches 50cm, the product reaction is very thorough, the tap density is high, and no oxygen-deficient spinel lithium manganate is generated. Meanwhile, in order to prepare spherical porous trimanganese tetroxide with better quality, a special device is designed to prepare the spherical porous trimanganese tetroxide.
In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of spherical porous manganous-manganic oxide comprises the following steps:
a. placing the spherical manganese oxide in a reduction furnace;
b. heating the reducing furnace at a heating speed of 1-10 ℃/min, introducing reducing gas in the heating process of the furnace, wherein the gas flow is 1-100L/h;
c. stopping heating after the set temperature is 400-900 ℃, keeping the temperature for 5-20 h in a reduction furnace, and naturally cooling to room temperature along with the furnace;
d. and (3) preserving the heat of the reduced manganese oxide in air or oxygen for 1-20 hours at the temperature of 150-400 ℃, and naturally cooling along with the furnace.
Preferably, the spherical manganese oxide is any one or a mixture of spherical manganous-manganic oxide and spherical manganous-manganic oxide, and the particle size of the manganese oxide ranges from 5 to 25 micrometers.
Preferably, the heating speed is 3-6 ℃/min.
Preferably, the set temperature is 500-700 ℃.
Preferably, the gas flow is 20-40L/h.
Preferably, the reducing gas is one or more mixed gases of other reducing gases such as high-purity hydrogen gas, hydrogen-argon mixed gas, methane and the like.
Further, the chemical reaction equation involved in the above preparation method is explained by using hydrogen as a reducing agent as follows:
(1) spherical manganic manganous oxide is used as a raw material:
Mn3O4+H2→MnO+H2O
(2) spherical manganese sesquioxide is taken as a raw material:
Mn2O3+H2→MnO+H2O
during reduction, water vapor is generated and plays a role in pore forming, and spherical porous MnO is generated. Further, the heating process in the air or the oxygen is carried out at the temperature of 150-400 ℃ for 1-20 h, preferably at the heating temperature of 300 ℃ for 10 h. Further, the porous manganese monoxide is heated in air or oxygen to generate spherical porous Mn3O4The reaction formula is as follows:
MnO+O2→Mn3O4
furthermore, the invention also relates to lithium manganate prepared by the spherical porous manganous-manganic oxide. Wherein, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium acetate and lithium oxalate, and lithium carbonate is preferred.
Fully mixing the spherical porous manganous-manganic oxide and lithium carbonate in a mixer according to the Li/Mn molar ratio of 1: 2, then putting the mixture into a kiln, wherein the material stacking thickness is 50cm, heating to 560 ℃ at the speed of 3 ℃/min, keeping the temperature for 5h, heating to 780 ℃ at the same speed, keeping the temperature for 24h, and cooling along with the kiln to obtain the spinel type lithium manganate.
A spherical porous manganous manganic oxide preparation device comprises a reduction furnace, a reduction gas tank, an oxidation gas tank, a base, a rack and a controller, wherein the reduction furnace, the oxidation gas tank and the reduction gas tank are arranged on the base, the reduction gas tank and the oxidation gas tank are communicated with the reduction furnace through a gas pipe, the reduction furnace comprises a heating cavity and a reduction cavity, the heating cavity is separated from the reduction cavity through a heat conducting pad, a heating element is arranged in the heating cavity, a sensor is arranged in the reduction cavity, a pressure release valve is also arranged at the same time, the reduction cavity is of a semi-surrounding structure with a hollow top, a rotating rod is contained in the reduction cavity, a plurality of material placing disks are arranged on the rotating rod, an elastic rotating part is arranged below the material placing disk close to the heat conducting pad, a cover plate is arranged at one end of the rotating rod, which is far away from the heat conducting pad, and the cover plate forms a sealing structure with the reduction cavity of the semi-surrounding structure through a sealing ring, the automatic reduction furnace is characterized in that a transmission piece is further arranged on the rotating rod and matched with the driving piece arranged on the frame, a heat insulation layer is further arranged outside the reduction furnace, and the controller controls all electrified devices of the equipment.
As a further improvement of the above technical solution:
the driving piece comprises a lifting cylinder, a connecting rod and a rotating motor which are arranged on the rack, the lifting cylinder is connected with one side of the connecting rod, and the rotating motor is connected with the other side of the connecting rod; the output end of the rotating motor is provided with a gear, and the gear is matched with the transmission piece for installation.
The elastic rotating piece comprises a spring, a bottom plate and rotating beads, one end of the spring is connected with the heat conducting pad, the other end of the spring is connected with one side of the bottom plate, and the rotating beads are uniformly arranged on the other side of the bottom plate.
Compared with the prior art, the invention has the following beneficial effects:
1. the raw materials for synthesizing the spherical porous manganous-manganic oxide of the invention are wide, and comprise any one or mixture of spherical manganous-manganic oxide and spherical manganous-manganic oxide.
2. The manganous-manganic oxide with the spherical porous structure prepared by the invention can ensure that the synthesized lithium manganate has high tap density; the pore structure of the spherical porous manganous-manganic oxide promotes the diffusion of oxygen in the bottom material, and when the material stacking thickness is 50cm, the material can still be completely converted into lithium manganate, and the tap density is high.
3. According to the preparation equipment for spherical porous trimanganese tetroxide, the reduction cavity is separated from the heating cavity, the reduction gas is not in direct contact with the heating cavity, the risks of deflagration and explosion are avoided, the charging tray is driven to rotate by the rotating rod, the uniform heating is ensured, and meanwhile, the large-batch product processing can be realized.
Drawings
FIG. 1 is a schematic structural diagram of a spherical porous mangano-manganic oxide preparation device.
Fig. 2 is a partial structural view of fig. 1.
FIG. 3 is a scanning electron microscope image of spherical porous manganese monoxide obtained in example 1 of the present invention.
FIG. 4 is a scanning electron microscope image of the pore structure of the spherical porous manganese monoxide obtained in example 1 of the present invention.
FIG. 5 is a scanning electron micrograph of spherical porous trimanganese tetroxide obtained in example 1 of the present invention.
FIG. 6 is a scanning electron microscope image of the pore structure of spherical porous trimanganese tetroxide obtained in example 1 of the present invention.
FIG. 7 is a scanning electron micrograph of spherical lithium manganate obtained according to example 1 of the present invention.
FIG. 8 is a schematic diagram of X-ray diffraction pattern (XRD) of the sample in a sintering sagger of example 1 of the present invention, wherein the sample comprises the upper part, the middle part and the bottom part.
Figure 9 XRD analysis results of example 1.
The invention
Reference numerals: 1. a reduction furnace; 2. a reduction gas tank; 3. an oxidation gas tank; 4. a base; 5. a frame; 6. A controller; 7. an air tube; 11. a heating cavity; 12. a reduction chamber; 13. a thermally conductive pad; 14. rotating the rod; 15. Placing a tray; 16. an elastic rotating member; 17. a cover plate; 18. a seal ring; 111. a heating member; 121. a sensor; 122. a pressure relief valve; 123. a thermal insulation layer; 141. a transmission member; 161. a spring; 162. a base plate; 163. Rotating the beads; 511. a lifting cylinder; 512. a connecting rod; 513. rotating the motor; 514. a gear member.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
Referring to fig. 3 to 9, this embodiment provides a method for preparing spherical porous manganous-manganic oxide and a method for preparing lithium manganate by using spherical porous manganous-manganic oxide, comprising the following steps:
a. spherical manganous-manganic oxide powder with the average grain diameter of 5 mu m is placed in a reduction furnace;
b. heating the reduction furnace at a heating rate of 3 ℃/min, introducing reducing gas which is hydrogen in the process of heating the furnace, wherein the gas flow is 10L/h;
c. stopping heating after the temperature reaches the set temperature of 450 ℃, preserving heat for 5 hours by using a reduction furnace, and naturally cooling to room temperature along with the furnace;
d. and (3) keeping the temperature of the reduced manganese oxide in the air for 10 hours at the temperature of 200 ℃, and naturally cooling along with the furnace. Spherical porous manganous-manganic oxide with the particle size of 5 mu m is obtained, and the width of the pore channel reaches 0.8 mu m.
Fully mixing the spherical porous manganous-manganic oxide and lithium carbonate in a mixer according to the Li/Mn molar ratio of 1: 2, then putting the mixture into a kiln, wherein the material stacking thickness is 50cm, heating to 560 ℃ at the speed of 3 ℃/min, keeping the temperature for 5h, heating to 780 ℃ at the same speed, keeping the temperature for 24h, and cooling the furnace to obtain the spinel type lithium manganate. The tap density of the obtained lithium manganate reaches 2.8g/cm3。
Example 2
The embodiment provides a preparation method of spherical porous manganous-manganic oxide. The method comprises the following steps:
a. spherical manganese sesquioxide powder with the average grain diameter of 15 mu m is placed in a reduction furnace;
b. heating the reduction furnace at a heating rate of 6 ℃/min, introducing reducing gas which is hydrogen in the process of heating the furnace, wherein the gas flow is 50L/h;
c. stopping heating after the set temperature is 600 ℃, preserving the heat of the reduction furnace for 10 hours, and naturally cooling the reduction furnace to room temperature;
d. and (3) keeping the temperature of the reduced manganese oxide in the air for 10 hours at the temperature of 300 ℃, and naturally cooling along with the furnace. Spherical porous manganous-manganic oxide with the particle size of 15 mu m is obtained, and the width of the pore channel reaches 0.8 mu m.
Fully mixing the spherical porous manganous-manganic oxide and lithium carbonate in a mixer according to the Li/Mn molar ratio of 1: 2, then putting the mixture into a kiln, wherein the material stacking thickness is 50cm, heating to 560 ℃ at the speed of 3 ℃/min, keeping the temperature for 5h, heating to 780 ℃ at the same speed, keeping the temperature for 24h, and cooling the furnace to obtain the spinel type lithium manganate. The tap density of the obtained lithium manganate reaches 2.8g/cm3。
Example 3
The embodiment provides a preparation method of spherical porous manganous-manganic oxide. The method comprises the following steps:
a. putting the mixed powder of spherical manganous-manganic oxide and spherical manganous-manganic oxide with the average grain diameter of 25 mu m into a reduction furnace;
b. heating the reduction furnace at a heating rate of 8 ℃/min, introducing reducing gas which is hydrogen in the process of heating the furnace, wherein the gas flow is 40L/h;
c. stopping heating after the set temperature reaches 800 ℃, keeping the temperature of the reduction furnace for 6 hours, and naturally cooling the reduction furnace to room temperature;
d. and (3) keeping the temperature of the reduced manganese oxide in the air for 1h at the temperature of 350 ℃, and naturally cooling along with the furnace. Spherical porous manganous-manganic oxide with the particle size of 25 mu m is obtained, and the width of the pore channel reaches 0.8 mu m.
Fully mixing the spherical porous manganous-manganic oxide and lithium carbonate in a mixer according to the Li/Mn molar ratio of 1: 2, then putting the mixture into a kiln, wherein the material stacking thickness is 50cm, heating to 560 ℃ at the speed of 3 ℃/min, keeping the temperature for 5h, heating to 780 ℃ at the same speed, keeping the temperature for 24h, and cooling the furnace to obtain the spinel type lithium manganate. The tap density of the obtained lithium manganate reaches 2.8g/cm3。
The spherical porous manganous-manganic oxide prepared by the invention has the following advantages that can be obtained from the examples 1 to 3:
(1) the raw materials for synthesizing the spherical porous mangano-manganic oxide are wide and comprise any one or a mixture of the spherical mangano-manganic oxide and the spherical mangano-manganic oxide.
(2) The high tap density of the lithium manganate prepared by the conventional mangano-manganic oxide is 2.1g/cm at most3The data of the examples prove that the manganous manganic oxide with the spherical porous structure can ensure that the synthesized lithium manganate has high tap density.
(3) The spherical porous mangano-manganic oxide has developed pore channels, and the width of the pore channels can reach 0.8 mu m;
(4) the pore channel structure of the spherical porous mangano-manganic oxide promotes the diffusion of oxygen at the bottom of the material, and when the material stacking thickness is 50cm, the material can be completely converted into manganeseThe tap density of lithium carbonate reaches 2.8g/cm3。
Example 4
As shown in fig. 1 to 2, the present embodiment provides a spherical porous manganous-manganic oxide preparation apparatus, which includes a reduction furnace 1, a reduction gas tank 2, an oxidation gas tank 3, a base 4, a frame 5, a controller 6, wherein the reduction furnace 1, the oxidation gas tank 3 and the reduction gas tank 2 are mounted on the base 4, wherein the reduction gas tank 2 and the oxidation gas tank 3 are communicated with the reduction furnace 1 through a gas pipe 7, the reduction furnace 1 includes a heating chamber 11 and a reduction chamber 12, the heating chamber 11 is separated from the reduction chamber 12 through a thermal pad 13, the thermal pad 13 is an environment-friendly material capable of resisting high temperature of 100 ℃, a heating element 111 is disposed in the heating chamber 11, the heating element 11 is an electric heating wire or other heating equipment, a sensor 121 is disposed in the reduction chamber 12, the sensor 121 is a temperature sensor mainly used for sensing the internal temperature of the reduction chamber, and a pressure release valve 122 is also disposed, the pressure release valve 122 is used for balancing the internal pressure of the reduction chamber 12, reducing the possibility of explosion. The reduction chamber 12 is the semi-surrounding structure of top fretwork, its inside has held dwang 14, install a plurality of blowing dishes 15 on the dwang 14, it installs elastic rotation piece 16 to be close to the blowing dish 15 below of heat conduction pad 13, the one end that heat conduction pad 13 was kept away from to the dwang 14 is provided with apron 17, apron 17 forms seal structure through sealing washer 18 and semi-surrounding structure's reduction chamber 12, still be provided with driving medium 141 on the dwang 14, driving medium 141 and the driving piece cooperation of setting in frame 5, reduction furnace 1 still is provided with insulating layer 123 outward, insulating layer 123, be used for keeping warm, it is extravagant to reduce the energy. The controller 6 controls all live devices of the apparatus.
The driving part comprises a lifting cylinder 511, a connecting rod 512 and a rotating motor 513 which are arranged on the rack, the lifting cylinder 511 is connected with one side of the connecting rod 512, and the rotating motor 513 is connected with the other side of the connecting rod 512; the output end of the rotating motor 513 is provided with a gear element 514, the gear element 514 is matched with the transmission element 141, and the transmission element 141 is a gear.
The elastic rotation member 16 includes a spring 161, a bottom plate 162, and a rotation ball 163, wherein one end of the spring 161 is connected to the thermal pad 13, the other end is connected to one side of the bottom plate 162, and the rotation ball 163 is uniformly disposed on the other side of the bottom plate 162.
The working principle is as follows: the user is when the user is at the user equipment, at first, weigh appropriate amount spherical oxides of manganese and put into blowing dish 15, reduction gas pitcher 2 lets in hydrogen through the trachea in to reduction chamber 12, the intracavity is discharged to the gas in reduction chamber 12, lift cylinder 511 downstream, gear 514 and driving medium 141 cooperate, apron 17 pushes down simultaneously, reduction chamber 12 forms the enclosure space, heating member 111 of heating chamber 11 inside heaies up the reduction chamber, when reaching the uniform temperature, sensor 121 can convey information for controller 6 control heating member 111's intensification, dwang 14 can be rotated through the driving part drive by driving medium 141 simultaneously, can make inside intensification in the rotatory process even, oxides of manganese homogeneous reduction simultaneously. And after the reduction is finished, naturally cooling to room temperature along with the furnace. After 10 minutes, oxygen or air is introduced into the reduction cavity 12 through the oxidation gas tank 3, (the oxygen and the hydrogen are mixed in a high-temperature state and are easy to explode, so that the hydrogen is discharged from the reduction cavity within 10 minutes, at the moment, inert gas can be introduced into the reduction cavity to exhaust the hydrogen completely), the lifting cylinder 511 moves upwards, the reduction cavity 12 is heated after the closed state is removed, at the moment, the rotating motor 513 continues to drive the rotating rod 14 to move, and the oxidation and the heating are uniform. After furnace cooling is completed, the driving member is disengaged from the transmission member 141, and the finished product is taken out. This equipment is through indirect heating, gaseous not direct and heating source contact, has reduced the potential safety hazard of gaseous existence in the intensification process, is provided with relief valve 122 simultaneously, can automatic pressure release when reducing chamber 12 internal pressure is too big make inside reach steady state. According to the equipment for preparing the spherical porous trimanganese tetroxide, the heating cavity is separated from the reduction cavity, so that the safety of the reduction and oxidation processes is ensured, the driving piece of the reduction cavity ensures that the manganese oxide is uniformly heated and reduced in the heating process, the residual product rate is lower than 0.01 percent, good conditions are provided for preparing the spherical porous trimanganese tetroxide, and high-quality raw materials are provided for preparing lithium manganate.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.